Cardiac leads may be endocardial leads, such as leads for sensing/pacing in right heart cavities, or leads introduced in the coronary network, notably leads comprising an electrode positioned in front of a left cavity of the myocardium.
The insertion of the latter type of leads, carried out through endocavitary approaches, is a particularly tricky intervention, taking into account the difficult access to the coronary sinus entrance via the right atrium, and also the required accuracy for the pacing sites once the lead is guided to its desired location and immobilized within the coronary network.
One of the implantation techniques of such a lead requires an accessory known as “guide-catheter”. This accessory comprises a hollow tubular sheath reinforced by a wire mesh and with an inner surface presenting a low coefficient of friction (for example, a surface made with PTFE, extruded or co-molded with the rest of the sheath). In addition, the sheath is designed to present a flexibility allowing a stiffness in torsion high enough to allow transmission of a rotational movement applied at one end to the other end, so as to allow guiding the lead tip within the myocardium during the procedure.
Once in place, the guide-catheter serves as a direct “tunnel” between the “external world” and the coronary sinus, a tunnel that can be utilized by the surgeon for sliding the lead therethrough to its final target site.
Once the lead is in place, the guide-catheter needs to be extracted. The extraction procedure is tricky because the lead must not be displaced, or its position or orientation altered as a result of the extraction.
One other difficulty of this extraction step is due to the presence of the electrical connector, at the proximal end of the lead: the diameter of this connector being greater than that of the internal lumen of the guide-catheter, it prevents the guide-catheter from being withdrawn by being simply slid backwardly along the lead.
The step of extracting the guide-catheter therefore usually requires it to be cut, starting from its proximal end and along a generatrix line by means of a slitting tool, also known as “slitter,” for slitting the proximal end of the catheter and reinforcement wire mesh forming the frame of the hollow sheath.
With one hand, the surgeon then pulls the guide-catheter towards him with a continuous gesture, while firmly maintaining the lead and the slitting tool with the other hand, allowing the slitting tool to simultaneously slit the sheath as it is being thus extracted.
It has already been proposed in the prior art, in order to avoid resorting to a sharp cutting tool, to use a non-reinforced sheath that is simply strippable; however, cutting of such a sheath along its whole length leads to a weakness and a lower rigidity of the guide-catheter, with a risk of folding and lower transmission of efforts (forces) during its setting up preparatory to an intervention event. It has also been proposed, notably by European patent EP 1,155,710 and its U.S. counterpart U.S. Pat. No. 6,625,496 (commonly assigned herewith to ELA Medical), to provide the lead with a removable connector, which avoids having to cut the guide-catheter. This method however leads to an increasing number of steps required for setting up and assembling the different elements, and also renders the intervention procedure more complicated.
Therefore slitting/cutting of the guide-catheter is, in practice, the most usual way to proceed.
One additional difficulty of this type of intervention comes from the presence, at the proximal end of the guide-catheter, of a hemostatic valve allowing to obdurate at will the internal lumen emerging from the proximal end, opened, of the guide-catheter.
This valve is usually provided with a lateral way (i.e., a passageway) able to communicate with the inner lumen of the guide-catheter, so as to allow purging the guide-catheter after its setting in place, and also eventually injecting therein an antithrombotic agent or radio contrast medium.
This hemostatic valve must meet several requirements, adding to the difficulties explained above. Firstly, the hemostatic valve must be able to allow the lead to pass through it, in order to make the lead penetrate into the guide-catheter then guide it up to its final position. Secondly, once the lead has been set in place, the valve has to be able to be dissociated from the guide-catheter, notably in order to allow the surgeon to initiate the cutting of the guide-catheter sheath so as to extract the latter.
Various configurations of guide-catheter/hemostatic valve sets have been already proposed in the prior art.
In U.S. Pat. No. 6,159,198 (Gardeski), the valve is a removable valve, fit into a coupling bell or “hub” through a Luer Lock type assembly, the hub being formed at the proximal end of the guide-catheter. Closing of the valve is ensured by a screwing mechanism located in the rear area of the valve and allowing to create at will a passage to the inner lumen in order to allow lead insertion. In order to allow cutting of the guide-catheter at the end of the intervention after removal of the valve, the coupling bell is also divisible (cuttable) following a thinner part formed along a generatrix and continued by a transition toward the reinforced sheath.
U.S. published patent application 2005/0,010,238 (Potter) discloses a hemostatic valve mounted at the tip of a guide-catheter on a coupling bell by means of a clipped assembly system. Differently from the Gardeski device, the coupling bell is not divisible (i.e., a bladed tool is required for cutting it), but frangible (i.e. it can be broken into two parts through a force exerted by the fingers of the surgeon, without the need for any additional tool). Once the coupling bell has been thus removed, the proximal end of the guide-catheter is directly accessible, allowing the cutting thereof by means of a usual method using a cutting tool.
U.S. published patent application 2004/0,176,781 (Lindstrom) discloses a toolkit for implanting a lead for a guide-catheter that is not reinforced, but simply strippable, and therefore does not require any cutting tool for its extraction. However, the procedure is rendered more complicated due to the need for resorting to an additional accessory known as TVI or dilator, in order to open the filling element of the valve and protect the lead during the passing through thereof. The dilator also allows increasing the rigidity of the strippable sheath, but of course it also has to be extracted after being used, which requires an additional step in the procedure, the dilator having to also be provided with a strippable structure.
U.S. Pat. No. 6,966,896 (Kurth) describes a toolkit for implanting a lead wherein the valve itself, instead of the coupling bell, is frangible. This allows separating the valve in two parts—the valve initially forming a single block with the guide-catheter—in order to let the proximal tip of the guide-catheter appear, and allow its cutting and extraction.
U.S. published patent application 2007/0123825 describes a toolkit implementing an introducer provided with a valve which can be dissociated in two halves, which are then able to be separated in order to allow peeling the introducer (which can therefore be extracted without the need for a cutting tool). The valve further comprises a means allowing, through pinching the two winglets of the valve, to open, level with the proximal end, an axial hole giving access to the lumen of an axial tubular part that is continuing the introducer. The catheter, provided with the lead, can then be inserted into this hole of the introducer.
All the various devices that have been proposed so far, however, suffer from several difficulties, particularly among them are the following:                there is always an existing significant risk, during the intervention, of a lead displacement at the moment when the valve is removed and the guide-catheter extracted, especially with those leads that are provided with an electrical connector having a large diameter, as all the accessories that are part of the introducing toolkit have to be removed over this connector;        the valves that are driven by a screw system require that the surgeon has a very accurate dexterity in order to prevent from damaging the lead by squeezing it too much and, reversely, from creating a lack of tightness during the intervention, due to an insufficient squeezing;        in the case of a divisible coupling bell, cutting thereof by means of a standard slitter is difficult, due to the brutal variation of the cutting force during the transition between the material of the bell and the reinforced sheath, with a risk of displacing the lead if the forces exerted by the surgeon are not well accurately balanced;        due to their simplicity, the frangible systems allow an easy removal of the valve, but have the drawback of not comprising any practical mechanism for driving the valve, thus oblige resorting to a dilator for introducing the lead in the valve; this accessory is “floating around” along the lead conductor during the intervention, and anyhow will have to be removed by means of peeling at the end of the intervention;        the frangible valves that are made as a single block with the guide-catheter, do not allow the surgeon to turn the lateral way around the guide-catheter;        all the solutions proposed up to now require a certain number of accessories or separate elements, which renders the surgeon's operation more complicated, during the critical step of the guide-catheter extraction, when the surgeon has to be focused on maintaining the position of the lead;        as the lead has to pass through all these accessories, notably the dilator, the lead electrodes may become polluted, especially by the lubricant usually utilized with the valve.        